Optically active glass and optical fiber with reduced photodarkening and method for reducing photodarkening

Abstract

An optically active glass and an optical fiber comprising such glass, having reduced photodarkening properties are provided. The optically active glass is mainly composed of silica representing from about 50 to 98 mol % of the glass. It also includes at least one active ion, such as a rear-earth ion, which induces a photodarkening effect in optical properties of the glass. Moreover, the glass includes an effective amount of phosphorus oxide providing the photodarkening reducing effect, preferably in an amount of from about 1 to 30 mol %. A method for reducing a photodarkening effect in optical properties of an optically active glass including the step of introducing phosphorus oxide to the glass is also provided.

Description

FIELD OF THE INVENTION[0001]The present invention relates to the field of optically active glass and more particularly concerns optically active glass and optical fibers in which photodarkening effects are reduced or eliminated.BACKGROUND OF THE INVENTION[0002]Optical fiber lasers and amplifiers used in the amplification of optical signals usually include optical fibers having optically active waveguiding cores doped with rare-earth active ions, such as for example, erbium, ytterbium and thulium. For such applications and others, it is important that the optical properties of the fiber remain stable. However, for some rare-earth doped core compositions, the formation of photoinduced structural transformations which can induce excess loss in the doped glass core of the fibers are observed over time under light illumination or propagation, resulting in reduced output power efficiency of the fibers. This phenomenon is known as photodarkening. It is a very detrimental effect, that decre...

AI Technical Summary

Benefits of technology

[0008]It is an object of the present invention to provide an optically active glass and an optical fiber having reduced photodarkening properties.

[0009]In accordance with a first aspect of the invention, there is provided an optically active glass including from about 50 to 98 mol % of silica, from 0.01 to about 5 mol % of at least one active ion inducing a photodarkening effect in optical properties of the optically active glass, and an effective amount of phosphorus oxide for reducing the photodarkening effect.

[0013]In accordance with yet another aspect of the invention, there is provided an optical fiber including an optically active glass including from about 50 to 98 mol % of silica, from 0.01 to about 5 mol % of at least one active ion inducing a photodarkening effect in optical properties of the glass, and an effective amount of phosphorus oxide for reducing the photodarkening effect.

[0016]In accordance with yet another aspect of the invention, there is provided a method for reducing a photodarkening effect in optical properties of an optically active silica glass including at least one active ion inducing the photodarkening effect. The method includes the step of doping the optically active glass with an effective amount of phosphorus oxide.

Problems solved by technology

However, for some rare-earth doped core compositions, the formation of photoinduced structural transformations which can induce excess loss in the doped glass core of the fibers are observed over time under light illumination or propagation, resulting in reduced output power efficiency of the fibers.

It is a very detrimental effect, that decreases for instance the output power of fiber laser or amplifier over time and make them inefficient.

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